Smoking in pregnancy is associated with increased total maternal serum cell-free DNA levels

Objective: Cell-free DNA is a marker of cellular apoptosis and necrosis. We wished to determine if maternal smoking affects maternal and fetal serum cell-free DNA levels. Methods: Case-control sets of stored second-trimester serum-screening samples from 27 smoking and 90 nonsmoking pregnant women were developed. Smoking status was confirmed by measuring serum cotinine levels. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and DYS1 levels were determined using real-time polymerase chain reaction (PCR) to measure total and fetal cell-free DNA, respectively. At delivery, medical records were reviewed to confirm gender and determine other factors that could affect DNA values. Results: Smoking was associated with significantly elevated GAPDH levels compared with nonsmokers (median: 97 662 genome equivalents (GE)/mL vs 38 217 GE/mL; p = 0.018). DYS1 levels were not statistically significantly elevated in smokers (p = 0.29). Other factors that affected DYS1 levels included maternal age in nonsmokers only (r² = 0.30, p = 0.013) and maternal Synthroid use (p = 0.0045) Conclusion: Pregnant smokers have threefold higher levels of total cell-free DNA compared with pregnant nonsmokers. Maternal age and Synthroid exposure may also affect circulating cell-free fetal DNA levels.